1. Field of the Invention
The present invention generally relates to a chuck which is to be attached to a plastic packaging bag, and a plastic packaging bag with a chuck, which utilizes the same.
2. Description of the Prior Art
Plastic chucks are easy to be repeatedly open and closed. For that reason, plastic chucks are attached to practical plastic packaging bags (which will be also hereinafter referred to as xe2x80x9cpackaging bagsxe2x80x9d) for many uses. Such a chuck has an opening/closing mechanism based on a zipper or bite. Most of chucks have an opening/closing mechanism based on a bite.
FIG. 7 is an illustration showing a conventional packaging bag with a chuck. This packaging bag 70 is provided with a chuck 71 which runs the length (shown by L in FIG. 7) of the inside face of an opening of the packaging bag 70.
FIG. 8 is a perspective view of a bite-type chuck which is provided on the packaging bag 70. The chuck 80 is designed to open and close the packaging bag 70 by the engagement and release of the male claw portion 81a of a male member 81 with and from the female claw portions 82a, 82a of a female member 82. The chuck 80 is fixed to the packaging bag 70 by fixing the base portions 81c and 82c of the male member 81 and female member 82 to the base material film of the packaging bag 70 by the heat seating (heat fusion).
Although the mechanism of the chuck 80 for closing the packaging bag 70 by means of the male and female claw portions 81a, 82a and 82a may be expressed by the term xe2x80x9cbiting mechanismxe2x80x9d, xe2x80x9cfitting mechanismxe2x80x9d, xe2x80x9cengaging mechanismxe2x80x9d, xe2x80x9clocking mechanismxe2x80x9d or the like, these terms may be used to be technically synonymous with each other. Throughout the specification, the term xe2x80x9cbitexe2x80x9d will be used hereinafter. Although the chucks 71 and 80 may be expressed by the term xe2x80x9cbiting devicexe2x80x9d, xe2x80x9cfitting devicexe2x80x9d, xe2x80x9cengaging devicexe2x80x9d or the like, these terms may be used to be technically synonymous with each other. Throughout the specification, the term xe2x80x9cchuckxe2x80x9d will be used hereinafter.
FIG. 9 is a cross-sectional view of another chuck which has been conventionally proposed. In this chuck, the male claw portion 90a of a male member 90 is designed to partially contact and engage the female portions 91a, 91a of a female member 91.
FIG. 10 is a cross-sectional view of a further chuck which has been conventionally proposed (see Japanese Patent Laid-Open No. 9-37816, etc.). In this chuck, the rounded male claw portion 100a of a male member 100 and the female claw portion 101a of a female member 101 are designed to have a bite. The chuck shown in FIG. 10 relates to a proposal wherein intermediate layers 102 and 103 are provided between polyester packing bag base material films which are generally difficult to be head-sealed.
FIG. 11 is also a cross-sectional view of a still further chuck which has been conventionally proposed. In this chuck, the outside projecting portions of the double male claw portions 110a, 110a of a male member 110, which vertically project from the surface of the male member 110 and which extend in parallel to each other, are designed to contact and engage the female claw portions 111a, 111a of a female member 111.
In most of conventional general chucks, part of male and female claw portions are designed to contact and engage each other so as to have inferior sealing performance in order to ensure a practical smooth opening/closing operation (e.g., see FIGS. 8, 9 and 11). In addition, since the male and female members of the chucks are molded by the profile extrusion molding method, the chucks can be formed by the profile extrusion molding method, and the male and female members are formed of a thermoplastic which is easily heat-sealed (see Japanese Patent Laid-Open No. 9-37816, etc.).
On the other hand, there is a tendency for packaging bags, such as refrigerating preserving bags and electronic oven heating bags, to be generally formed of a base material film having heat resistance, cold resistance and other characteristics (e.g., a polyamide (e.g., nylon 12) or a polycapramide (e.g., nylon 6)), so that it is difficult to fix conventional chucks to such packaging bag base material films by the heat sealing.
For that reason, the development of chucks has been generally directed to the improvement of base material films, which are difficult to be heat-sealed, and fixing means (see Japanese Patent Laid-Open Nos. 9-37816, 9-156646, 9-94931, 9-216642, etc.), so that chucks have been generally attached to packaging bags for goods which do not require sealing performance. In the circumstances, a chuck capable of blocking liquid has been studied and proposed (see Japanese Patent No. 293878).
FIG. 12 is a cross-sectional view of a chuck having high liquid blocking performance (see Japanese Patent No. 293878, page 5, FIG. 1). In this chuck, the double male claw portions 120a, 120a of a male member 120, which vertically project from the surface of the male member 120 and which extend in parallel to each other, are designed to be pushed by a pressing rib 120b to strongly contact and engage the female claw portions 121a, 121a of a female member 121. In the experiment wherein a packaging bag with the chuck shown in FIG. 12 is filled with water to be dropped from a height of 30 cm, water does not leak out (see Japanese Patent No. 293878, page 4, Example and Table 1). However, in the chuck shown in FIG. 12, the male claw portions 120a, 120a are deformed as a whole during bite, so that there is some possibility that distortion may occur in the male claw portions 120a, 120a by repeatedly opening and closing the chuck. Conventionally, even in the chuck realizing liquid blocking performance shown in FIG. 12 (see Japanese Patent No. 293878), any contact mechanism in a contact portion in which the male claw portions contact the female claw portions has not been studied, and it is only suggested that a line contact or a surface contact can obtain target sealing performance (see Japanese Patent No. 293878, page 2).
With the advance of technology, packaging bags of a base material film having high gas impermeability (e.g., a film having gas impermeability which is increased by selecting the kind of a raw material and laminating) come into wide use, and are used for various goods (e.g., foods, medicines and so forth which deteriorate in the presence of oxygen) which essentially require gas impermeability (generally air impermeability).
However, it has been considered that the sealing performance of the chuck is limited to the blocking of liquid, and there has been no idea that gas blocking performance is given to the chuck, so that the gas blocking performance of the chuck has not been studied and proposed. In addition, the details of the contact mechanism of the male and female claw portions during the bite of the chuck have not been studied.
Therefore, the inventor studied the details of the contact mechanism of male and female claw portions during the bite of a chuck, and found that a chuck having sealing performance, such as gas blocking performance, can not be obtained unless both of line and surface contacts exist.
It is therefore a principal object of the present invention to eliminate the aforementioned problems and to provide a chuck which has sealing performance, such as gas blocking performance capable of blocking various gases, and which is capable of being smoothly open and closed, the sealing performance of the chuck being held after the chuck is repeatedly open and closed, and the chuck being capable of being easily produced and easily fixed to a base material film of a packaging bag by the head sealing.
It is another object of the present invention to provide a chuck capable of causing a packaging bag to serve as an airtight container.
It is a further object of the present invention to provide a plastic packaging bag with a chuck, which has a housing region (typically, an airtight housing region) isolated from external environment and which is capable of being easily open and closed.
In order to accomplish the aforementioned and other objects, according to one aspect of the present invention, there is provided a chuck for a plastic packaging bag, the chuck comprising: a male member having a male claw portion; a female member having a female claw portion; and a mechanism for causing the male claw portion to engage and disengage from the female claw portion, wherein one of the male claw portion and the female claw portion has one or more linear protrusions which extend in longitudinal directions in a contact portion in which the male claw portion engages the female claw portion, and wherein the male claw portion contacts the female claw portion in the contact portion by a line contact, by which the one or more linear protrusions of the one of the male claw contact the other claw portion of the male claw portion and the female claw portion and by a surface contact, by which that the male claw portion contacts the female claw portion.
According to another aspect of the present invention, there is provided a plastic packaging bag with a chuck which comprises a male member having a male claw portion, a female member having a female claw portion, and a mechanism for causing the male claw portion to engage and disengage from the female claw portion, wherein one of the male claw portion and the female claw portion has one or more linear protrusions which extend in longitudinal directions in a contact portion in which the male claw portion engages the female claw portion, and wherein the male claw portion contacts the female claw portion in the contact portion by a line contact, by which the one or more linear protrusions of the one of the male claw contact the other claw portion of the male claw portion and the female claw portion and by a surface contact, by which that the male claw portion contacts the female claw portion, the plastic packaging bag being formed of a gas impermeable plastic film as a base material film.